Photographic color developing compositions are used to process color photographic materials such as color photographic films and papers to provide the desired color images. Such compositions generally contain color developing agents, for example 4-amino-3-methyl-N-(.beta.-methane sulfonamidoethyl)aniline, as reducing agents to react with suitable color forming couplers to form the desired dyes. However, such color developing agents are susceptible to oxidation by dissolved oxygen. Therefore, an antioxidant is conventionally included in the color developer compositions to preserve the oxidation state of the color developing agent and thereby maintain useful color developer activity.
Many classes of compounds have been employed as color developer solution antioxidants, including hydroxylamines, hydroxamic acids, oximes, nitroxy radicals, hydrazines, hydrazides, phenols, saccharides, various simple amines, polyamines, quaternary ammonium salts, alpha-hydroxy ketones, alcohols, diamides and disulfonamides. To be used in practice, however, antioxidants must be soluble in aqueous media, non-toxic to living organisms, low cost and non-silver halide developers. Further, it is desirable that antioxidants react slowly with oxygen and rapidly with oxidized color developer, but not so rapidly that color development is retarded. Yet another concern is that the antioxidant must not be able to promote bacterial growth.
All of these considerations greatly limit the number and classes of compounds that practically can be used as antioxidants or stabilizers in color developer solutions. One class of compounds often used as antioxidants are hydroxylamines. They exhibit excellent characteristics by having a slow rate of aerial oxidation, being non-silver halide developers, and relatively inexpensive to produce. There are considerable publications describing such compounds.
While there is considerable literature describing various hydroxylamines that can be used as antioxidants, most of them have a number of disadvantages. For example, making them with certain solubilizing groups may be difficult or expensive. In addition, even when generally water-soluble, they may still emit an unpleasant odor that is offensive to users in the photoprocessing industry. Given the growth of photoprocessing in mini-lab processors in highly populated places such as supermarkets and malls, it is highly desirable that the color developers be as odor free as possible.
U.S. Pat. No. 4,892,804 (Vincent et al) describes a number of dialkylhydroxylamines useful as color developer antioxidants, including N,N-diethylhydroxylamine, which are improvements over the unsubstituted or mono-substituted hydroxylamines. U.S. Pat. No. 4,876,174 (Ishikawa et al) describes a lengthy list of substituted hydroxylamines believed useful as antioxidants in color developer compositions, but the compounds actually used emit unpleasant odors.
In U.S. Pat. No. 5,354,646 (Kobayashi et al), water-solubilizing groups, such as carboxy and sulfo are shown on dialkylhydroxylamines. Certain cyclic hydroxylamines are described in U.S. Pat. No. 5,660,974 (Marrese et al).
As the antioxidants shown in the art have varying and unpredictable effects, there remains a need to find relatively inexpensive, odorless and consistently effective antioxidants for color developer compositions.